Effect of Amount of Leaching Water and Method of Calcium Application on the Reclamation of a Saline Sodic Soil
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Abstract:
A saline-sodic soil (pH 10.0, ESP 100.0) rich in soluble sodium carbonate was packed in 32 cm long acrylic plastic columns and leached with calcium chloride applied as slug at the soil surface and as dissolved salt in leaching water itself (solution application). For similar amounts of water, the application of Ca as a slug removed sodium up to a greater soil depth than its addition in the form of solution. Increase in the amount of water applied in case af slug increased the depth up to which the exchangeable sodium in the soil was lowered below 15%. With similar amounts of Ca, dilute solutions removed more exchangeable sodium from the soil. The results have been interpreted in terms of simultaneous movement of Na and Ca and change in their concentrations down the profile during reclamation.Keywords:
Sodic soil
Sodium carbonate
Saline water
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A laboratory column experiment was conducted to study the effect of sodic waters on behaviour of native Si and P during reclamation of sodic soils. Three soils varying in pH i.e. reclaimed (pH 8.4), partially reclaimed (pH 9.2) and unreclaimed sodic soil (pH 10.2), were leached with 2, 4 and 8 pore volumes of sodic waters of 2.5, 5.0 and 10.0 me L−1 RSC under constant water head. Silicon and P concentrations in the leachates were measured periodically. In high pH soil, infiltration rate was less and it took almost 10 times more time to pass the same volume of leachate as compared to that in low pH soils. Silicon losses increased significantly with increase in RSC of applied water irrespective of the initial pH of the soil, the extent of loss varied with the initial pH and silica content of the soil. Maximum loss of Si as well as of P occurred in unreclaimed sodic soil.
Sodic soil
Infiltration (HVAC)
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SUMMARY Gypsum application was highly efficient as a treatment for reducing amounts of exchangeable sodium and inhibiting clay dispersion in highly structured saline‐sodic clay topsoils. Phosphogypsum, applied to the surfaces of aggregates in soil columns treated with simulated rainfall, was dissolved efficiently by frequent intermittent ‘rainfall’. The calcium released by dissolution displaced sodium on the exchange complex within soil aggregates ranging from 7.5 mm to 45 mm in diameter. Of the applied calcium, 64–74% was transferred to ion exchange sites; however, almost one‐third of this adsorbed calcium displaced exchangeable magnesium. Comparison of three gypsum treatments, phosphogypsum, rock gypsum, and a saturated gypsum solution (representing a top dressing of highly soluble gypsum), showed that the effectiveness of calcium uptake on the exchange complex followed the order: rock gypsum < saturated solution < phosphogypsum, but differences were small. Application of phosphogypsum caused a 90% reduction in the total amount of dispersed clay released in column leachates, and decreased the maximum clay concentration in the effluents by at least 80%, when compared to soils leached without gypsum treatment.
Phosphogypsum
Sodic soil
Sodium adsorption ratio
Cation-exchange capacity
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Abstract Despite the low mobility in soil, surface liming has increased plant growth and yield. Since only the topsoil is affected by this technique, the benefits may be caused by improvements in soil solution. This experiment aimed to assess chemical changes in the solid phase and leached solutions after addition of calcitic limes to a Humic Hapludox. Calcium carbonate or calcium hydroxide was throughly mixed with soil samples at rates of 0, 0.25, 0.50, 1.0, and 1.50-times that required to raise soil pH to 6.0 (equivalent to 0, 3.5, 7.0, 14, and 21 t ha−1). After 60 days, treated samples were transferred to the top (30 cm) of leaching columns, filled with unlimed soil in the bottom (23 cm). Water was percolated weekly through the columns during 12 weeks. Chemical determinations were performed on all leached solutions, and at different soil depths below the limed layer at the end of the experiment. Calcium (Ca), magnesium (Mg), and aluminum (Al) increased linearly in the percolated solution with increases...
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Cation-exchange capacity
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Effect of leaching two artificially prepared sodic soils, one rich in chloride and the other in bicarbonate ions with gypsum solutions was evaluated in the laboratory. The soils packed in acrylic columns were leached with gypsum solutions of three different concentrations, keeping the total amount of gypsum same in all the treatments. A greater decline in ESP and pH was observed with decrease in Ca concentration in leaching solutions. Leaching with 20 cm solution of 30 m.e./l Ca concentration followed by 40 cm distilled water proved better than any other treatment in bicarbonate treated soil but in chloride treated one its effect was equivalent to leaching with 20 cm solution of 30 m.e./l concentration. The decrease in EC was a function of total amount of solution/water passing through the columns in both the soils.
Distilled water
Bicarbonate
Sodic soil
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The kind and amount of ions released from soil and consequent changes in composition of applied waters were estimated in sandy loam alkali soil of pHs 9.2, sodium adsorption ratio (SAR) 31.9 and electrical conductivity (ECe) 3.2 dS m−1. The soils were equilibrated with waters having three levels of total electrolyte concentration (TEC) (TEC: 10, 20 and 40 m.e. L−1), four levels of SAR (10, 20, 30 and 40) and two levels of residual sodium carbonate (RSC: 0 and 5 m.e. L−1). The analysis of effluent collected at equilibrium showed that Na followed by Ca+Mg were the major cations and CO3 and HCO3 were the major anions released, as a result of which total salt concentration increased by 4.0 to 7.0 m.e. L−1 compared to applied waters. Owing to the proportionately higher release of Ca+Mg, effluent SAR was drastically reduced by 6 to 72%, particularly where initial total electrolyte concentration of water was low and SAR was high. Higher release of CO3+HCO3 than Ca+Mg increased RSC of the effluent by 0.2 to 1.7 m.e. L−1. To find out the ions released from mineral weathering, previously equilibrated soil columns were again leached uniformly with pore volumes of good quality water having SAR 1.5 and TEC 6.1 m.e. L−1 at biweekly intervals till the steady composition of coming out solution was achieved. Here also a continuous released Na varied from 3.9 to 6.8 m.e. L−1 and that of Ca+Mg varied from 0.8 to 1.2 m.e. L−1 in the displaced soil solution at steady state. From break-through curves, it was found that the relative release of Na in soil solution from soil, saturated with waters of different SAR and TEC, both of RSC and non-RSC, was higher and continued for longer duration than Ca+Mg. Though more Na was released than Ca+Mg but ratio of Na:Ca+Mg ions released into the soil solution varied only from 3.5 to 6.8 which would reduce the sodic hazards (SAR) of irrigation waters having SAR > 9.6. The release of Ca+Mg reduced sodic hazards of high SAR irrigation water, which will not be as high as suggested by their chemical composition.
Sodium adsorption ratio
Dilution
Sodium carbonate
Alkali soil
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Abstract A laboratory study was conducted with 2 objectives: i. to determine the effects of salinization on the cation composition of saturation paste and soil solution extracts and ii. to determine the accuracy with which the saturation extract, the traditionally used method, reflects the composition of the soil solution, the ionic medium in which plant roots reside. A factorial experiment including 5 sulfate salt species each applied at 5 rates was established in a loamy sand soil and the composition of the 2 extracts was determined after equilibration. Na and Mg concentrations in both the soil solution and saturation extract were directly related to amounts of these cations applied. K concentrations tended to increase with increasing salt concentration because of release of sorbed K. Ca concentration in both extracts was increased by addition of low levels of salt (< 200 mmol/L), apparently by release of exchangeable Ca, but decreased with higher salt addition because of precipitation reactions. The decline in Ca concentration, which is exacerbated by a simultaneous decrease in activity coefficient, may have been sufficient to induce Ca deficiency and restrict crop yields. The estimated Ca activity declined from approximately 10 mmol/L to 2 mmol/L with increasing amounts of salts applied. The saturation extract provided an accurate measure of the Na, Mg, and total salt concentration of the soil solution, regardless of the type of salt applied. In contrast, Ca concentration in the soil solution was not accurately reflected by analysis of the saturation extract. The ratio of Ca to total cations in the soil solution, however, which is closely related to crop yield in sulfate‐dominated saline soils, was highly correlated to the same ratio in the saturation extract.
Saturation (graph theory)
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Abstract Sodic soils exhibit poor physical conditions that adversely influence water and air movement, soil erodibility, and plant growth. This study investigated the efficiency of naturally occurring CaCO 3 in reclaiming a sodic loess soil (Calcic Haploxeralf) with an exchangeable sodium percentage of 16. Soil columns (50 or 100 mm high) were leached with distilled water (DW), 1 dS m ‐1 tap water (TW), or CO 2 ‐enriched TW at a flow rate of either 11.5 or 50 mm h ‐1 . The effluent from the columns was collected continuously, and its chemical composition was analyzed. When DW was used, CaCO 3 dissolution was the main source (85%) for replacing exchangeable Na. When TW was used, 80% of the (Ca 2+ + Mg 2+ ) for reclaiming the sodic soil came from the leaching solution. The slow water flow rate (11.5 mm h ‐1 ) improved reclamation by ∼30%, probably due to the higher concentration of (Ca 2+ + Mg 2+ ) from CaCO 3 and the longer time available for Ca 2+ diffusion into soil aggregates. The CO 2 ‐enriched TW was the most favorable treatment for CaCO 3 dissolution and thus the most efficient for soil reclamation. Our results suggest that reclamation of sodic soils can be accomplished by means of the naturally occurring CaCO 3 in the soil, providing management conducive for CaCO 3 dissolution is used.
Sodic soil
Distilled water
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Abstract Fully hydrolysed poly (vinyl alcohol) (PVA) with molecular weight 14000 was effective in reducing or preventing clay dispersion when columns of mixed sand/Na‐soil aggregates containing a wide range of NaCl salt contents were leached with distilled water. The maximum effect was obtained over a range of soil salt contents in which the applied polymer remained soluble. Above this range, because of polymer precipitation, effectiveness was inversely related to salt content. For soil aggregates with different exchangeable sodium percentage (ESPs), PVA was also effective in reducing or preventing dispersion in water and maintaining the relative hydraulic conductivity of soil columns leached successively with diluted solutions. However, a further relationship was found which showed that the polymer was more effectively incorporated in soils with higher ESP. This was reflected in measurements of dispersion and may be explained by the greater effect of drying (at 70°C) and by the greater adsorption of PVA in the presence of exchangeable sodium than exchangeable calcium.
Distilled water
Vinyl alcohol
Sodium adsorption ratio
Bentonite
Sodic soil
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Abstract Phosphorus (P) availability to plants in reclaimed alkali soils was the main objective of this study, which was also focused on P transformations, decrease in Olsen‐P content, and magnitude of P lost in leachate in course of amendment application and leaching. Liquid sodium bicarbonate (NaHCO3) was added to nonalkali soils to set up four ESP (exchangeable sodium percentage) levels (viz., 2.9, 25.0, 50.0, and 75.0), but actual ESP levels obtained were 2.9, 24.6, 51.2, and 75.3. Amendments (viz., gypsum and pyrites) and P treatments (viz., 0 and 50 mg P Kg−1) were mixed with dry, sieved soil before filling into PVC (polyvinyl chloride) drainage columns, which were then compacted to uniform bulk density and leached with deionized water for 30 days. Results indicated that the pH and electrical conductivity (EC) of the soils increased with increase in ESP level of the soil but decreased with amendment application. Phosphorus addition to alkali soils decreased the pH on day 30, but it could not affect the EC of the soils. Successive increase in the ESP level of the soil increased the pH and EC off the leachate. Gypsum‐amended soils exhibited lower pH and EC values than pyrite‐amended soils. The EC of the leachate decreased sharply with time in amended soils, but the pH decreased slowly. Phosphorus addition affected the leachate pH earlier than the soil pH. Cumulative volume of leachate decreased with increasing ESP levels, but it increased with amendment and phosphorus application. Leaching of P increased with increase in ESP levels, and the maximum cumulative loss of P was 11.2 mg Kg−1 in the 75.3 ESP soil. Cumulative P lost in the pyrite‐amended soils was higher than the gypsum‐amended soils. Phosphorus leaching in the gypsum‐amended soils stopped at day 10 and beyond, but it continued until day 30 in the pyrite‐amended soils. Part of the applied P in alkali soils was also lost along with the native P, whereas it was protected in the nonalkali soils. OlsenP increased with increasing ESP levels, and alkali soils invariably contained higher Olsen P than nonalkali soils. At day 30, alkali soils contained much higher Olsen P (12.6 mg Kg−1) than nonalkali soils (5.9 mg Kg−1). In general, there was a decrease in the Olsen P with both of the amendments, but it decreased more with pyrites than with gypsum. Phosphorus added through monopotassium phosphate (KH2PO4) remained extractable by Olsen's extractant up to day 30. Results also indicated that percent distribution of ammonium chloride (NH4Cl)‐P, calcium (Ca)‐P, and unknown P increased with rising ESP levels but iron (Fe)‐aluminum (Al)‐bound P and residual P decreased. Percent distribution of Ca‐P and unknown P exhibited an increase with time also. Unamended alkali soils contained more NH4Cl‐P than amended ones. Iron and Al‐ bound P and residual P increased more with pyrites, whereas formation of Ca‐P and unknown P was enhanced with gypsum. Applied P tended to convert more into NH4Cl‐P, Ca‐P, and residual P than to Fe‐Al‐bound P or unknown P fractions. Models developed to estimate Olsen P and P concentration in leachate, through pH or EC, have application value for P management in alkali soils that are leached after application of amendments. Keywords: Exchangeable sodium percentagephosphorussalt Acknowledgements S.M.Misra express his deep sense of gratitude to the Director, Indian Grassland and Fodder Research Institute, Jhansi, for granting the study leave for completion of the project and to the Indian Council of Agricultural Research, New Delhi, for awarding the senior research fellowship to meet the contingent requirements. S.M.Misra is also indebted to Biplav Misra for his involvement in the project from the very beginning and his assistance in data‐management procedures and model fitting and for critical reading of the manuscript.
Amendment
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